1. Technical Field
The present invention relates to a composition for manufacturing contact lenses. More particularly, the present invention relates to a composition for manufacturing contact lenses comprising a silicone polymeric material with hydrophilic functional end-caps having excellent oxygen permeability and water content.
2. Description of Related Art
The hydrogel contact lenses are made from hydrogel materials, such as poly-2-hydroxyethyl methacrylate (p-HEMA), which can be improved in strength by adding crosslinking agent like ethylene glycol dimethacrylate (EGDMA). Since the water content of the p-HEMA is only about 38.8%, the hydrophilic monomer, for example N-vinylpyrrolidone (NVP), N,N-dimethylacrylamide (DMA) and methyl acrylic acid, is added to improve the water content of such materials for the contact lenses. With the addition of the hydrophilic monomer, the water content of the contact lenses can increase up to 80%. However, the higher water content of the contact lenses is, the lower tension and toughness thereof become. Therefore, the water content of contact lenses is generally controlled in the range from about 45% to 58%.
Silicone hydrogel contact lenses comprise a hydrophilic silicone polymeric material which was made by polymerizing two siloxane macromers, which have different chemical structures and different molecular weights, and a hydrophilic monomer, such as N-vinylpyrrolidone (NVP), methyl acrylic acid (MAA) and N,N-dimethylacrylamide (DMA).
However, due to the hydrophobic characteristic on the surface of silicone hydrogel contact lenses, it is apt to incur the bacteria breed and eyes irritation. Therefore, it demands to provide a composition of contact lenses and a method for manufacturing contact lenses with enhancing the hydrophilicity of the contact lenses.